Find root of the tree where children id sum for every node is given | C # Find root of tree where children sum for every node id is given . ; Every node appears once as an id , and every node except for the root appears once in a sum . So if we subtract all the sums from all the ids , we 're left  with the root id. ; Driver code
using System ; class GFG { public class pair { public int first , second ; public pair ( int first , int second ) { this . first = first ; this . second = second ; } } static int findRoot ( pair [ ] arr , int n ) { int root = 0 ; for ( int i = 0 ; i < n ; i ++ ) { root += ( arr [ i ] . first - arr [ i ] . second ) ; } return root ; } public static void Main ( String [ ] args ) { pair [ ] arr = { new pair ( 1 , 5 ) , new pair ( 2 , 0 ) , new pair ( 3 , 0 ) , new pair ( 4 , 0 ) , new pair ( 5 , 5 ) , new pair ( 6 , 5 ) } ; int n = arr . Length ; Console . Write ( " { 0 } STRNEWLINE " , findRoot ( arr , n ) ) ; } }